Conjugated polymers have been a major focus of scientific and technological research during the past few decades due to their potential use as semiconductors and electroactive materials in organic electronics, particularly in thin film transistors, photovoltaic cells, and light-emitting devices. See, e.g., Sirringhaus, H. et al., Science, 280: 1741-1744 (1998). Among these, organic thin film transistors (OTFTs) are considered viable alternatives to more traditional, mainstream transistors based on inorganic materials because they combine the advantages of large area coverage, low costs, and structural flexibility. See, e.g., Horowitz, G., Adv. Mater., 10: 365-377 (1998). Transistors are the key components used for amplification and switching in all modern electronics. Two important device performance metrics of organic transistors are the charge carrier mobility (μ) and current on/off ratio (Ion/Ioff).
Although charge carrier mobilities are approaching 1 cm2V−1s−1 for n-type and 10 cm2V−1s−1 for p-type molecular semiconductors, the mobility values for polymeric semiconductors still remain one to two orders of magnitude below these values. See, e.g., Dimitrakopoulos, C. D. et al., Adv. Mater., 14: 99-117 (2002). Design, synthesis, and characterization of new π-conjugated polymeric semiconductors for OTFTs are of great interest due to the intrinsic technological attributes of polymers, such as compatibility with simple direct-write printing techniques, ease of film formation, compatibility with low-cost manufacturing processes and compatibility with flexible plastic circuits. See, e.g., Zhu, Y. et al., Macromolecules, 38: 7983-7991 (2005). Although mobilities as high as 0.1 cm2 V−1s−1 have been obtained for p-type polymers (see, e.g., Sirringhaus, H. et al., Nature, 401: 685-687 (1999)), soluble n-type polymers are rare, with the highest reported mobility using practical conditions approaching only 10−6 cm2 V−1s−1. Although a mobility of 0.1 cm2 V−1 s−1 has been reported for an n-type polymer, this was achieved only after post-solution-casting modifications, a procedure that is not practical for general applications. See, e.g., Babel, A. et al.; J. Am. Chem. Soc., 125: 13656-13657 (2003).